Method of heat treating oil



Patented Nov. 20, 1934 UNITED STATES PATENT OFFICE 1,981,826 v METHOD oF HEAT TREATING on.

Ware

Application June 19, 1931, Serial No. 545,418

7 Claims.

This invention relates to improvements in the heat treatment of hydrocarbon oil. The invention will be fully understood from the following I description taken in connection with the accom- 5 panying drawing in which latter the figure is a longitudinal sectional view through a furnace showing a heating coil suitable for carrying out the invention.

Referring particularly to thedrawing, reference numeral 1- designates a furnace having suitable burners 2 by means of .which flame is injected into the heating chamber of the furnace. A coil of tubing 3 is suitably supported in the heating chamber of the furnace in position to receive heat by radiation and convection. The coil is provided with an inlet end 4 which is adapted to receive from a pump 5 hydrocarbon oil under greater ,than atmospheric pressure ranging from over 60 pounds per square inch to approximately 1,400 pounds per square inch.-

The coil is provided with a discharge end. 7

through 'which the heated hydrocarbon oil is adapted to be discharged to a suitable place for further treatment, not shown. A valve 8 is provided in the discharge end 7 whereby the oil can be maintained under the greater than atmospheric pressures within the coil. In passing from the inlet through the successive bends of the coil, the hydrocarbon oil becomes heated by the transfer of heat from the heating chamber through the walls of the tubing and into the body of oil owing through 'the tubing. The walls of the tubing are formed of steel or other suitable material capable of withstanding the high` temperatures and greater than atmospheric pressures. The walls of the tubing are of substantial thickness whereby they can withstand the pressure of the oilunder the elevated temperatures used. The oil passing through the first stages of the coil is at a considerably lower temperature than the temperature of the hot gases in the chamber surrounding the tubing, and the portion of the Walls of the tubing adjoining the oil is at a lower temperature than the portion of the Walls of the tubing adjoining the surroundinghot gases.

Inlet tubes 10 open into an intermediate portion of the coil and are adapted to convey an oxidizing gas into the coil under pressure of a 50 pump or compressor 11 at a pressure at least as great as the pressure of oil within the coil, which oxidizing agent may be pre-heated by coil 12 to approximately or somewhat higher than the oil temperature at the points of introduction of the former into the hydrocarbon coil. Any suitable vthe heated oil in amounts to accelerate the rise -intemperature of the oil to approximately 950 to v oxidizing gas can be injected into the oil in the -proximately 850 F. by the application' of external heat only. -The oxidizing -gas causes a rapid oxidation reaction to occur within the oil with the formation of carbon dioxide, Water and other products and with the evolution ofl suflcient vheat to raise the temperature of the entire body of oil with great rapidity.

The gaseous oxidizing agent is introduced into 1100 F. due to the partial combustion. Preferably approximately 15 cubic feet of air are used per gallon of oil and at least one percent of the oil is burned with a result that the rate of rise of temperature of the oil is greatly accelerated. It is easy by this method to at least doublethe rate of rise of the preheated oil to a rapid cracking temperature. The application of external heat may or may not be continued through-out the extent of passage of the oil through the cracking coil. In the embodiment illustrated, the portion of the coil containing oil at a temperature of 850 F. and higher is in a region ofreduced external heat input.

By the process as outlined the factors of time and temperature in cracking are controlled to a greater extent than can be done by heating the oil through external surfaces such as tubes. It will be understood that the rate of heat input through tubes sets a limit to the rate of heating and the temperature which can be reached before excessive cracking takes places. Byl causing the cracking reaction to occur at relatively high temperatures, a relatively high quality of product is obtained and also by the use of relatively high pressures upon the oil undergoing cracking a relatively great distribution is obtained between the gasoline and dissipated products such as coke and gas. The above mentioned factors are controlled by eifecting partial combustion within the oil under treatment and Without being limited by the heat and pressure stresses which are allowable for heating tubes. In order to initiate the combustion at the time and temperature where its value can be used to greatest advanl05 tage, the combustion is initiated when only a small percentage of cracking has occurred. This percentage varies with the particular oil undergoing treatment. l

By way of example, a Mid-Continent gas oil llo "l substantially higher knock rating than would have been obtained had the oil been heated through tubes to a light conversion. At the same time the gas losses and tar produced have been reduced substantially 50%.

By the procedure described, the maximum amount o! cracking occln's at the highest temperatures of the cracking coil and the time interval during which most of the production of wrelatively light hydrocarbon, such as gasoline, oc-

curs is materially reduced. The loss of gasoline due to the formation of dissipative products is minimized since the cracking is carried out rapidly at relatively high temperatures. The oil is passed through the dissipative temperature zone which is effective between approximately 750 F.

and 1,000 F. without allowing time for appreciable low temperature cracking. The product obtained has a relatively high knock rating.

There is a diminished requirement for heat input through the walls of the tubing and a marked decrease of stresses due to uneven expansion of the material of the tubing walls which would otherwise be caused by extreme unequal temperatures within and without the tubing. A prolonged length of life for the tubing is obtained. The.

rapid rise in the temperature of the oil due to oxidation in the portion of the coil which is subjected to the highest temperatures in the furnace tends to equalize the temperatures of the inner and outer portion of the tubing walls at this portion of the coil and therefore minimizes the stresses within the tubing walls.

Various changes may be made within the scope of the appended claims in which it is desired to claim all novelty inherent in the invention as broadly as the prior art permits.

We claim: 1. The method of cracking hydrocarbon oil, which comprises heating an oil stream under 5 greater than atmospheric pressure to a cracking temperature of not more than approximately 850? F. by the application of external heat only and without substantial decomposition, and injecting a gaseous oxidizing agent into the heated oil stream in amounts to at least double the rate ofrise in temperature of the oil to approximately 950 to 1100 F. by partial combustion.

2. The method of cracking hydrocarbon oil, which comprises heating a stream of oil under greater than atmospheric pressure to a cracking temperature of not more than approximately 850 F. by the application of external heat only and without substantial decomposition, and injecting a gaseous oxidizing agent into the heated oil stream in amounts to burn at least one percent of the oil whereby the temperature of the oil is rapidly raised to approximately 950 to 1100 F.

3. The method of cracking hydrocarbon oil, which comprises heating a stream of oil to a cracking temperature of not more than approximately 850 F. by the application of external heat only and without substantial decomposition, and injecting approximately fteen cubic feet of -air per gallon of oil into the heated oil stream to eiect partial combustion of the oil while continuing the application of externall heat whereby the temperature of the oil is rapidly raised to approximately 950 to 1100 F and reaction is substantially entirely accomplished at such temperature.

4. In the heat treatment of hydrocarbon oil, the steps which comprise passing the hydrocarbon oil through an elongated narrow heating zone, exteriorly applying heat to the zone whereby the temperature of the oil is raised to a low cracking temperature but Without substantial cracking, then injecting a gaseous oxidizing agent into the heated oilA in an intermediate portion of the heating zone in amounts suilicient to burn at least 1% of the oil to raise the temperature to a rapid cracking temperature, and permitting reaction at such temperature.

5. In the heat'treatment of hydrocarbon oil, 100 the steps which comprise passing the hydrocarbon, oil through an elongated narrow heating zone, exteriorly applying heat to the zone whereby the temperature of the oil is raised to a low cracking temperature but without substantial cracking, then injecting approximately 15 cubic feet of air per gallon of oil into the heated oil -in an intermediate portion of the heating zone whereby a certain portion of the oil is burned and its temperature raised to a rapid cracking temperatture, and permitting reaction at such temperaure.

6. In the heat treatment of hydrocarbon oil, the steps which comprise passing the hydrocarbon oil through an elongated narrow heating zone, exteriorly applying heat to the zone whereby the temperature of the oil is raised to a low cracking temperature without substantial decomposition, maintaining the oil under greater than atmospheric pressure, injecting a gaseous oxidizing l agent into the stream of heated oil in an intermediate portion of the heating zone in amounts sumcient to burn at least 1% of the oil whereby its temperature is raised to a rapid cracking temperature, and permitting reaction at such teml. perature.

7. In the heat treatment of hydrocarbon oil, the steps which comprise passing the hydrocarbon oil through an elongated narrow heating zone, exteriorly applying heat to the zone whereby the temperature of the oil is raised to a low cracking temperature without substantial decomposition, maintaining the oil under greater than atmospheric pressure, injecting approximately 15 cubic feet of air per gallon of oil into the stream of heated oil in an intermediate portion of the heating zone whereby a certain portion of the foil is burned and its temperature raised to a rapid cracking temperature, and permitting reaction at such temperature.

EDWARD B. PECK. CARL E. KLEIBER. 

